1. Field of the Invention
The present invention relates generally to manual transmissions and, more particularly, to a manual transmission for a vehicle.
2. Description of the Related Art
Generally speaking, land vehicles require three basic components. These components comprise a power plant (such as an internal combustion engine), a power train, and wheels. The internal combustion engine produces force by the conversion of chemical energy in a liquid fuel into the mechanical energy of motion (kinetic energy). The function of the power train is to transmit this resultant force to the wheels to provide movement of the vehicle.
The power train's main component is typically referred to as the “transmission”. Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. The vehicle's transmission is also capable of controlling the direction of rotation being applied to the wheels, so that the vehicle may be driven both forward and backward.
It is known to provide a manual transmission for a vehicle such as a truck. The manual transmission typically includes an input shaft, a counter shaft, and an output shaft, and a plurality of gear set pairs that selectively provide various gear ratios, or relationships between the input and output shafts. The output shaft is in meshed engagement with the counter shaft with the gear set pairs operatively disposed between the input shaft and the counter shaft. Typically, driver gears of the gear set pairs are mounted to the counter shaft and a headset is disposed prior to the gear set pairs. Additionally, in transmissions for trucks and other heavy utility vehicles, the conventional manual transmissions are designed with greater numbers of gear ratios and gear sets. This requires a plurality of synchronizers to selectively engage respective gears to the counter shaft.
One disadvantage of this conventional approach to truck and heavy vehicle transmissions is that all of the driver gears are placed on the counter shaft and the headset increases torque on the counter shaft. As a result, the driver gears on the counter shaft receive increased load, necessitating the driver gears to be relatively large in size for the necessary strength. Another disadvantage is that all the synchronizer controlled gears on only one of the shafts requires a large axial length to include all the operative parts and accommodate the axial room necessary to move the synchronizers in and out of engagement. Further, the long axial length of the shafts either requires additional bearings for support or causes the end bearings to be separated over the length of the shafts. Adding intermediate bearings along the shafts to compensate further adds to overall shaft length. Conversely, a long shaft length without intermediate bearing support causes the shafts to be subject to bending and deflection. If this possible bending is countered by strengthening the shafts, then all the components will have additional size, weight, and associated cost. Furthermore, long shafts resulting from the placement of all of the synchronized gears on one shaft requires that very strong shifting forces have to be applied to engage the gear pairs.
In addition, many applications in trucks and other heavy vehicles require a power take-off as a source of motive power for any number of various power driven attachments and accessories that may be connected to the transmission or the vehicle. In providing a power take-off, the transmissions of the prior art have generally employed separate power take-off shafts that interconnect to the drive gears or assemblies within the transmission. However, the addition of a separate shaft requires a number of additional components that add to the size, weight, and complexity of the transmission.
Therefore, it is desirable to provide a new manual transmission for a vehicle that provides all driver gears on an input shaft to receive only engine torque. It is also desirable to provide a manual transmission that reduces the number of parts, the size of the transmission, and the cost. It is further desirable to provide a manual transmission that includes a power take-off that is integrated into the transmission and does not require a separate power take-off shaft. Therefore, there is a need in the art to provide a manual transmission that meets these desires.